Washington often visited Mount Vernon and Belvoir, the plantation that belonged to Lawrence's father-in-law William Fairfax. Fairfax became Washington's patron and surrogate father, and Washington spent a month in 1748 with a team surveying Fairfax's Shenandoah Valley property. The following year he received a surveyor's license from the College of William & Mary when he was 17 years old. Even though Washington had not served the customary apprenticeship, Fairfax appointed him surveyor of Culpeper County, Virginia, and he appeared in Culpeper County to take his oath of office July 20, 1749. He subsequently familiarized himself with the frontier region, and though he resigned from the job in 1750, he continued to do surveys west of the Blue Ridge Mountains. By 1752 he had bought almost 1,500 acres in the Valley and owned 2,315 acres.